It's hard to put your IT into USB mode. It happened to me too.

But here is how you do it after hooking up the USB cable and the
IT is off:

1. Push the "home" key, the bottom part not the top part!
2. Push the "power on/off" key
2. When you see the USB on the right corner of the screen, release the "home" key first. Now you should be in USB mode ready for flashing.


Good luck!